Wiring board and process for fabricating the same

ABSTRACT

A process for fabricating a wiring board is provided. In the process, a wiring carrying substrate including a carry substrate and a wiring layer is formed. Next, at least one blind via is formed in the wiring carrying substrate. Next, the wiring carrying substrate is laminated to another wiring carrying substrate via an insulation layer. The insulation layer is disposed between the wiring layers of the wiring carrying substrates and full fills the blind via. Next, parts of the carry substrates are removed to expose the insulation layer in the blind via. Next, a conductive pillar connected between the wiring layers is formed. Next, the rest carry substrates are removed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 97135492, filed on Sep. 16, 2008. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wiring board and a process forfabricating the same. More particularly, the present invention relatesto an embedded circuit board and a process for fabricating the same.

2. Description of Related Art

Embedded circuit boards are developed according to a current wiringboard technique, and circuits on a surface of such wiring board areembedded in a dielectric layer, and are not protruded out from a surfaceof the dielectric layer.

FIG. 1A to FIG. 1E are cross-sectional views illustrating a fabricationflowchart of a conventional embedded circuit board. Referring to FIG.1A, a method for fabricating the conventional embedded circuit boardincludes following steps. First, a copper metal layer 114 a and a copperwiring layer 116 a are sequentially formed on a carry substrate 112 a toform a wiring carrying substrate 110 a.

Referring to FIG. 1B, the wiring carrying substrate 110 a is laminatedon another wiring carrying substrate 110 b via a prepreg, wherein astructure of the wiring carrying substrate 110 b is the same to that ofthe wiring carrying substrate 110 a. In detail, the wiring carryingsubstrate 110 b also includes a carry substrate 112 b, a copper wiringlayer 116 b and a copper metal layer 114 b located between the copperwiring layer 116 b and the carry substrate 112 b. After the wiringcarrying substrate 110 a is laminated on the wiring carrying substrate110 b, the prepreg is cured to form a dielectric layer 120.

Referring to FIG. 1B and FIG. 1C, the carry substrate 112 a and thecarry substrate 112 b are removed to remain the copper metal layers 114a and 114 b, and the copper wiring layers 116 a and 116 b. Next, amechanical drilling process and a plating through hole (PTH) process aresequentially performed to form a conductive through hole structure T1.When the conductive through hole structure T1 is formed, a copperplating layer 130 a and a copper plating layer 130 b are respectivelyformed on the copper metal layer 114 a and the copper metal layer 114 b.

Referring FIG. 1C and FIG. 1D, etching is performed to remove the copperplating layers 130 a and 130 b, and the copper metal layers 114 a and114 b. Next, ink material 140 is filled into the conductive through holestructure T1.

Referring to FIG. 1D and FIG. 1E, after the ink material 140 is filled,a solder mask layer 150 a is formed on the copper wiring layer 116 a,and a solder mask layer 150 b is formed on the copper wiring layer 116b. By such means, fabrication of the conventional embedded circuit board100 is completed.

In the current wiring board technique, the embedded circuit board has adevelopment trend of high-density layout and fine lines. However, duringthe process of laminating the wiring carrying substrate 110 a to thewiring carrying substrate 110 b (referring to FIG. 1B), the prepreg isdeformed due to a press, which is referred to as shrink-swell in theart. Such deformation can generally change a whole dimensional scale ofthe embedded circuit board 100, and can also change a layout of thecopper wiring layers 116 a and 116 b and a relative position of theconductive through hole structure T1.

In the current wiring board technique, a kind of the deformationgenerated during the laminating process can change the relative positionbetween the layouts of the copper wiring layers 116 a and 116 b (whichis also referred to as layer-layer shifting in the art). Though, thedeformation that causes such layer-layer shifting can be properlycontrolled via a positioning apparatus of a lamination device, and arelative shifting amount thereof can be below 25 μm. Therefore,influence of the deformation generated due to the layer-layer shiftingcaused by the laminating process is greatly reduced.

The higher the layout densities of the copper wiring layers 116 a and116 b are, the greater the shrink-swell deformation influences thelayout of the copper wiring layers 116 a and 116 b, and the relativeposition of the conductive through hole structure T1. During themechanical drilling, since the layouts of the copper wiring layers 116 aand 116 b are changed, when a Muraki tooling system is applied, thethrough hole generated based on the mechanical drilling process isshifted, and even broken out (for example, the conductive through holestructure T2 in FIGS. 1C-1E).

The mechanical drilling process is taken as an example in theaforementioned conventional technique, though for the conductive blindvia generated based on a laser drilling technique, the break outphenomenon, the positioning apparatus and the positioning principle areall the same to that of the mechanical drilling process, and even therejection and a reason of the rejection are all similar, and thereforedetailed description thereof is not repeated.

SUMMARY OF THE INVENTION

The present invention is directed to a wiring board, and a fabricationprocess for making the same.

The present invention provides a process for fabricating a wiring board.First, a first wiring carrying substrate is formed, which includes afirst carry substrate and a first wiring layer disposed on the firstcarry substrate. Next, at least one first blind via is formed in thefirst wiring carrying substrate, wherein the first blind via extendsfrom the first wiring layer into the first carry substrate. Next, thefirst wiring carrying substrate is laminated to a second wiring carryingsubstrate via an insulation layer, wherein the second wiring carryingsubstrate includes a second carry substrate and a second wiring layerdisposed on the second carry substrate. The insulation layer is disposedbetween the first wiring layer and the second wiring layer, and fillsthe first blind via. Next, a part of the first carry substrate and apart of the second carry substrate are removed to expose the insulationlayer in the first blind via. Next, a part of the insulation layer inthe first blind via is removed to form a hole extending from the firstwiring layer to the second wiring layer. Next, a conductive pillar isformed in the hole, wherein the conductive pillar is connected betweenthe first wiring layer and the second wiring layer. Next, the remainedfirst carry substrate and the remained second carry substrate areremoved.

In an embodiment of the present invention, a method of forming the holeincludes thermally ablating a part of the insulation in the first blindvia by using a laser beam.

In an embodiment of the present invention, the laser beam is provided bya carbon dioxide laser device, an ultra violet laser device or a yttriumaluminium garnet (YAG) laser device.

In an embodiment of the present invention, a method of forming the holeincludes performing a mechanical drilling process.

In an embodiment of the present invention, the second wiring carryingsubstrate has at least a second blind via extending from the secondwiring layer to the second carry substrate. When the first wiringcarrying substrate is laminated on the second wiring carrying substrate,the insulation layer further fills the second blind via, and after apart of the second carry substrate is removed, the insulation layer inthe second blind via is exposed.

In an embodiment of the present invention, the second blind via isopposite to the first blind via. When a part of the insulation layer inthe first blind via is removed, a part of the insulation layer in thesecond blind via is also removed for connecting the first blind via andthe second blind via.

In an embodiment of the present invention, a method of forming the firstwiring carrying substrate includes following steps. First, a mask layeris formed on the first carry substrate, wherein the mask layer partiallycovers a surface of the first carry substrate. Next, the first wiringlayer and a barrier layer is formed, wherein the first wiring layer andthe barrier layer are located on the surface of the first carrysubstrate partially exposed by the mask layer, and the first wiringlayer is located between the barrier layer and the first carrysubstrate. The first wiring layer and the barrier layer wholly cover thesurface of the first carry substrate.

In an embodiment of the present invention, a method of forming the firstblind via includes removing a part of the mask layer to form at least anopening partially exposing the first carry substrate, and removing apart of the first carry substrate in the opening.

In an embodiment of the present invention, a method of removing a partof the mask layer includes removing a part of the mask layer by using alaser beam.

In an embodiment of the present invention, a method of removing thefirst carry substrate includes etching the first carry substrate.

In an embodiment of the present invention, after the first blind via isformed, the method further includes removing the barrier layer and theremained mask layer.

In an embodiment of the present invention, a method of forming the blindvia includes thermally ablating a part of the first carry substrate byusing a laser beam.

In an embodiment of the present invention, the insulation layer is aresin layer or prepreg.

The present invention provides a wiring board having at least a hole.The wiring board includes a first wiring layer, a second wiring layer,an insulation layer and at least a conductive pillar. The insulationlayer is disposed between the first wiring layer and the second wiringlayer, wherein the hole extends from the first wiring layer to thesecond wiring layer. The conductive pillar is disposed in the hole, andis connected between the first wiring layer and the second wiring layer,wherein the conductive pillar has a top surface and a bottom surfaceopposite to the top surface. The diameter of conductive pillar graduallyshrinks from a junction between the first wiring layer and theinsulation layer towards the top surface.

In an embodiment of the present invention, the conductive pillar fullfills the hole.

In an embodiment of the present invention, an interface is respectivelyexisted between the conductive pillar and the first wiring layer, andbetween the conductive pillar and the second wiring layer.

In an embodiment of the present invention, the hole is a blind via, andthe diameter of conductive pillar gradually shrinks from a junctionbetween the first wiring layer and the insulation layer towards thebottom surface.

In an embodiment of the present invention, the hole is a through hole,and the diameter of conductive pillar gradually shrinks from a junctionbetween the second wiring layer and the insulation layer towards thebottom surface.

In the present invention, at least one blind via (for example, the firstblind via) is preformed on the wiring carrying substrate (for example,the first wiring carrying substrate), and the insulation layer fullfills the blind via. Therefore, after a part of the carry substrate isremoved, the insulation layer in the blind via is exposed to serve asmarks for marking positions of later formed holes. By such means, achance of hole shifting can be reduced, so as to improve the productionyield of the wiring board.

In order to make the aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures is described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A to FIG. 1E are cross-sectional views illustrating a flowchart ofa conventional embedded circuit board fabrication process.

FIGS. 2A to FIG. 2G are cross-sectional views illustrating a fabricationflowchart of a wiring board according to an embodiment of the presentinvention.

FIG. 3A to FIG. 3G are cross-sectional views illustrating a fabricationflowchart of a wiring board according to another embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

FIGS. 2A to FIG. 2G are cross-sectional views illustrating a fabricationflowchart of a wiring board according to an embodiment of the presentinvention. Referring to FIG. 2A, the fabrication process of the wiringboard of the present embodiment can be described as follows. First, afirst wiring carrying substrate 200 a including a first carry substrate210 a and a first wiring layer 220 a is formed, wherein the first wiringlayer 220 a is disposed on the first carry substrate 210 a.

The first carry substrate 210 a can be a metal plate, which can be aplate formed by a single metal material, or a composite plate formed bymulti metal layers. As shown in FIG. 2A, the first carry substrate 210 ainclude two metal layers 212 a and 214 a, wherein material of the metallayer 212 a is for example, aluminium, nickel, tin, and material of themetal layer 214 a is for example, copper, aluminium, zinc, nickel orother metal materials having a high conductivity.

The first wiring layer 220 a can be formed by electroplating. In detail,a mask layer can be first formed on the first carry substrate 210 a,wherein the mask layer partially exposes the surface of the metal layer214 a, and the mask layer is for example a dry film after a lithographyprocess or a wet photoresist. Next, the first carry substrate 210 a iselectroplated to form the first wiring layer 220 a. After the firstwiring layer 220 a is formed, the mask layer is then totally removed.

Referring to FIG. 2B, a plurality of first blind via B1 and B1′ areformed on the first wiring carry substrate 200 a, wherein the firstblind via B1 and B1′ extends from the first wiring layer 220 a into thefirst carry substrate 210 a. Moreover, opening sizes of the first blindvia B1 and B1′ are greater than bottom sizes of the first blind via B1and B1′, as shown in FIG. 2B. The method of forming the first blind viaB1 and B1′ includes thermally ablating a part of the first carrysubstrate 210 a by using a laser beam, wherein the laser beam is forexample provided by an ultra violet laser device.

A difference between the first blind via B1 and the first blind via B1′is that depths thereof are different. In detail, a depth D1 of the firstblind via B1 is greater than a depth D2 of the first blind via B1′, andthe depth D1 is further greater than a thickness L of the metal layer214 a. The depth D2 of the first blind via B1′ is less than thethickness L of the metal layer 214 a, and the depth D2 can be greaterthan or equal to four-fifths of the thickness L.

It should be noted that though a plurality of the first blind via B1 andB1′ is illustrated in FIG. 2B, it is only an example, and in otherembodiments, only one first blind via B1 or one first blind via B1′ canbe formed. Namely, a total quantity of the first blind via B1 and B1′can be one. Therefore, the quantity of the first blind via B1 and B1′shown in FIG. 2B is not used for limiting the present invention.

Referring to FIG. 2C, the first wiring carrying substrate 200 a islaminated to the second wiring carrying substrate 200 b via aninsulation layer 310, i.e. the insulation layer 310 is disposed betweenthe first wiring layer 220 a and the second wiring layer 220 b.Moreover, the first wiring layer 220 a and the second wiring layer 220 bare all embedded into the insulation layer 310, as shown in FIG. 2C.

The second wiring carrying substrate 200 b includes a second carrysubstrate 210 b and a second wiring layer 220 b, wherein the secondwiring layer 220 b is disposed on the second carry substrate 210 b.Therefore, structure of the first wring carrying substrate 200 a issimilar to that of the second wiring carrying substrate.

The second carry substrate 210 b can be a plate formed by a single metalmaterial, or a composite plate formed by multi metal layers, andstructure of the second carry substrate 210 b is the same to that of thefirst carry substrate 210 a. In detail, the second carry substrate 210 bincludes two metal layers 212 b and 214 b, wherein the material of themetal layer 212 b can be the same to that of the metal layer 212 a, andthe material of the metal layer 214 b can be the same to that of themetal layer 214 a.

In the present embodiment, the second wiring carrying substrate 200 bhas at least one second blind via B2, wherein the second blind via B2extends from the second wiring layer 220 b into the second carrysubstrate 210 b. A depth of the second blind via B2 can be greater thana thickness of the metal layer 214 b, as shown in FIG. 2C. Certainly, inother embodiments that are not illustrated, the depth of the secondblind via B2 can be less than the thickness of the metal layer 214 b.

The second blind via B2 corresponds to one of the first blind via B1,i.e. the second blind via B2 is located opposite to one of the firstblind via B1. In other embodiments that are not illustrated, the secondblind via B2 can also correspond to one of the first blind via B1′.Namely, the second blind via B2 can be located opposite to one of thefirst blind via B1 or one of the first blind via B1′. Certainly, thesecond blind via B2 can also correspond to none of the first blind viaB1 and B1′. Moreover, a method of forming the second blind via B2 is thesame to that of the first blind via B1 and B1′, and therefore detaileddescription thereof is not repeated.

It should be noted that in the present embodiment, the second blind viaB2 is not a necessary technique feature of the present invention.Namely, the second wiring carrying substrate 200 b can have none secondblind via B2. Certainly, the second wiring carrying substrate 200 b canalso have a plurality of the second blind via B2. Therefore, thequantity of the second blind via B2 shown in FIG. 2C is only an example,which is not used for limiting the present invention.

When the first wiring carrying substrate 200 a is laminated to thesecond wiring carrying substrate 200 b, the insulation layer 310 fullfills the first blind via B1 and B1′ and the second blind via B2. Indetail, the insulation layer 310 can be a material with viscousness andmobility, for example resin or prepreg. Therefore, during thelamination, the insulation layer 310 can full fill the first blind viaB1 and B1′ and the second blind via B2.

Referring to FIG. 2C and FIG. 2D, a part of the first carry substrate210 a and a part of the second carry substrate 210 b are removed toexpose the insulation layer 310 in the first blind via B1. In detail,the method for removing a part of the first carry substrate 210 a and apart of the second carry substrate 210 b includes removing the metallayer 212 a and the metal layer 212 b. Since the depth of the firstblind via B1 is greater than the thickness of the metal layer 214 a, andthe depth of the second blind via B2 is greater than the thickness ofthe metal layer 214 b, after the metal layer 212 a and the metal layer212 b are removed, the insulation layer 310 located within the firstblind via B1 and the second blind via B2 is then exposed.

The method for removing the metal layer 212 a and the metal layer 212 bincludes etching the metal layer 212 a and the metal layer 212 b.Moreover, the first carry substrate 210 a and the second carry substrate210 b can be composite metal plates containing a polymer material layer.Therefore, the metal layer 212 a and the metal layer 212 b can beremoved by peeling.

Referring to FIG. 2D and FIG. 2E, a part of the metal layer 214 a can beremoved to form a metal layer 214 a′, so as to expose the insulationlayer 310 in the first blind via B1′. The method of removing a part ofthe metal layer 214 a includes etching the metal layer 214 a, forexample, performing a micro-etching by dipping the metal layer 214 ainto etching fluid.

It should be noted that in the method of removing a part of the firstcarry substrate 210 a and a part of the second carry substrate 210 bdisclosed in FIG. 2C to FIG. 2E, the step of FIG. 2D can be omitted inthe present embodiment, i.e. the step of removing a part of the metallayer 214 a. In detail, in the present embodiment, only the first blindvia B1 with depth being greater than the thickness of the metal layer214 a and the second blind via B2 with depth being greater than thethickness of the metal layer 214 b can be formed. In this case, afterthe metal layer 212 a and the metal layer 212 b are removed, theinsulation layer 310 located in the first blind via B1 and the secondblind via B2 is exposed. Therefore, the method of removing a part of thefirst carry substrate 210 a and a part of the second carry substrate 210b disclosed in FIG. 2C to FIG. 2E is only an example, which is not usedfor limiting the present invention.

Referring to FIG. 2E and FIG. 2F, after the insulation layer 310 locatedin the first blind via B1 and B1′ and the second blind via B2 isexposed, a part of the insulation layer 310 in the first blind via B1and B1′ is removed to form a plurality of holes H1 and H2. The holes H1and H2 are connected to the first blind via B1 and B1′. Moreover, theholes H1 and H2 extend from the first wiring layer 220 a to the secondwiring layer 220 b.

Structurally, the hole H1 is the blind via, i.e. the hole H1 does notpenetrate through the second wiring layer 220 b and the metal layer 214b. The hole H2 not only connects one of the first blind via B1, but alsoconnects the second blind via B2. Therefore, the hole H2 is the throughhole, structurally. Namely, the hole H2 penetrates through the secondwiring layer 220 b and the metal layer 214 b. In detail, when a part ofthe insulation layer 310 in the first blind via B1 and B1′ is removed, apart of the insulation layer 310 in the second blind via B2 can furtherbe removed to form the hole H2. Therefore, one of the first blind via B1is connected to the second blind via B2. Moreover, in other embodimentsthat are not illustrated, the first blind via B1′ can also be connectedto the second blind via B2.

Since a part of the insulation layer 310 is exposed in the first blindvia B1 and B1′ and the second blind via B2, the exposed part of theinsulation layer 310 can serve as marks for marking positions of theholes H1 and H2 to be formed. By such means, a chance of forming theholes H1 and H2 at wrong positions can be reduced, so as to avoidshifting of the holes H1 and H2, and improve the production yield of thewiring board.

Moreover, the method of forming the holes H1 and H2 includes thermallyablating the part of the insulation layer 310 in the first blind via B1and B1′ and the second blind via B2 by using the laser beam, or byperforming a mechanical drilling process. According to the method ofthermally ablating a part of the insulation layer 310 by using the laserbeam, in the present embodiment, a laser beam which can easily burn andvaporize the insulation layer 310 without damaging the first wiringlayer 220 a and the metal layer 214 a′ can be applied, for example, alaser beam provided by a carbon dioxide laser device. Therefore, thepart of the insulation layer 310 in the first blind via B1 and B1′ andthe second blind via B2 can be accurately removed to increase a chanceof forming the holes H1 and H2 at correct positions. Besides the carbondioxide laser device, the laser beam of the present invention can alsobe provided by an ultra violet laser device or a yttrium aluminiumgarnet (YAG) laser device.

Referring to FIG. 2F and FIG. 2G, a plurality of conductive pillars 320a and 320 b are formed in the holes H1 and H2, wherein the conductivepillars 320 a and 320 b are connected between the first wiring layer 220a and the second wiring layer 220 b. Namely, the first wiring layer 220a is electrically connected to the second wiring layer 220 b via theconductive pillars 320 a and 320 b. The conductive pillars 320 a and 320b are disposed in the holes H1 and H2. Each of the conductive pillars320 a has a top surface 322 a and a bottom surface 324 a, and theconductive pillar 320 b has a top surface 322 b and a bottom surface 324b. The top surface 322 a is opposite to the bottom surface 324 a, andthe top surface 322 b is opposite to the bottom surface 324 b.

Since opening sizes of the first blind via B1 and B1′ are greater thanbottom sizes of the first blind via B1 and B1′ (referring to FIG. 2B),influenced by structures of the first blind via B1 and B1′, thediameters of conductive pillars 320 a and 320 b gradually shrink from ajunction between the first wiring layer 220 a and the insulation layer310 towards the top surfaces 322 a and 322 b. Moreover, the diameters ofconductive pillars 320 a in the holes H1 gradually shrink from thejunction between the first wiring layer 220 a and the insulation layer310 towards the bottom surface 324 a, and the diameter of conductivepillar 320 b in the hole H2 gradually shrinks from a junction betweenthe second wiring layer 220 b and the insulation layer 310 towards thebottom surface 324 b, as shown in FIG. 2G.

In the embodiment of FIG. 2G, the holes H1 and H2 are full filled by theconductive pillars 320 a and 320 b, wherein the conductive pillars 320 aand 320 b are solid cylinders. However, in other embodiments that arenot illustrated, the holes H1 and H2 are not full filled by theconductive pillars 320 a and 320 b. Namely, the conductive pillars 320 aand 320 b can be hollow cylinders.

Methods of forming the conductive pillars 320 a and 320 b arediversified. In the present embodiment, the conductive pillars 320 a and320 b can be formed via an electroless plating process or anelectroplating process. Moreover, the conductive pillars 320 a and 320 bare not formed by a same fabrication process with that of the firstwiring layer 220 a and the second wiring layer 220 b. Therefore, even ifthe conductive pillars 320 a and 320 b, the first wiring layer 220 a andthe second wiring layer 220 b are all formed by the same material, aninterface I is still existed between the conductive pillars 320 a and320 b and the first wiring layer 220 a and the second wiring layer 220b, respectively. The interfaces I can be viewed via a microsectiontechnique with coordination of a general magnifier or an opticalmicroscope.

Referring to FIG. 2F and FIG. 2G, it should be noted that a quantity ofthe formed conductive pillars 320 b relates to a quantity of the secondblind via B2, and a quantity of the formed conductive pillars 320 asimultaneously relates to a quantity of the first blind via B1 and B1′and the second blind via B2. For example, if the total quantity of thesecond blind via B2 is one, the quantity of the formed conductive pillar320 b is also one. If the total quantity of the first blind via B1 andB1′ is M, and the total quantity of the second blind via B2 is N, thequantity of the formed conductive pillar 320 a is then equal to M-N.Therefore, the quantity of the conductive pillars 320 a and 320 b shownin FIG. 2G is only an example, which is not used for limiting thepresent invention.

After the conductive pillars 320 a and 320 b are formed, the remainedfirst carry substrate 210 a (for example the metal layer 214 a′ shown inFIG. 2F) and the remained second carry substrate 210 b (for example, themetal layer 214 b shown in FIG. 2F) are removed. Wherein, method ofremoving the metal layer 214 a′ and the metal layer 214 b includesetching the metal layer 214 a′ and the metal layer 214 b. Now,fabrication of a wiring board 300 including the first wiring layer 220a, the second wiring layer 220 b, the insulation layer 310 and aplurality of the conductive pillars 320 a and 320 b is completed.Moreover, after the wiring board 300 is completed, a solder mask layercan be formed on the first wiring layer 220 a and the second wiringlayer 220 b for protection.

FIG. 3A to FIG. 3G are cross-sectional views illustrating a fabricationflowchart of a wiring board according to another embodiment of thepresent invention. The present embodiment is similar to theaforementioned embodiment, and differences there between lie in thefabrication process of the wiring board. Therefore, only the differencesbetween the present embodiment and the aforementioned embodiment aredescribed in FIG. 3A to FIG. 3G and the following contents.

FIG. 3A and FIG. 3B mainly disclose a method of forming a first wiringcarrying substrate 400 a. Referring to FIG. 3A, a mask layer 430 isfirst formed on a first carry substrate 410 a, wherein the mask layer430 partially covers a surface S1 of the first carry substrate 410 a.

The mask layer 430 can be a dry film or a wet photoresist, and can beformed via a lithography process. The first carry substrate 410 a is forexample, a composite plate formed by multi metal layers, and the firstcarry substrate 410 a includes three kinds of metal layers 412 a, 414 aand 416 a, wherein the metal layer 412 a is disposed between two metallayers 416 a, and one of the metal layers 416 a is disposed between themetal layer 414 a and the metal layer 412 a. Moreover, materials of themetal layer 412 a and the metal layers 416 a are different.

The material of the metal layer 412 a can be aluminium, copper, tin orother metal materials having high strength and high toughness, and thematerial of the metal layer 414 a can be copper, aluminium, zinc, nickelor other metal materials having high conductivity. When the material ofthe metal layer 412 a is aluminium, the material of the metal layer 416a can be the metal material with lower activity compared to that of thealuminium, such as zinc, nickel or tin, so as to prevent the metal layer416 a from being damaged by chemical solutions such as etching fluid,etc. during fabrication process of the wiring board, and meanwhileinfluence of fabrication environment and reduction of production yielddue to damaging of the metal layer 416 a can be avoided.

Referring to FIG. 3B, a first wiring layer 420 a and a barrier layer 440are formed, wherein the first wiring layer 420 a and the barrier layer440 are located on the surface S1 of the first carry substrate 410 apartially exposed by the mask layer 430, and the first wiring layer 420a is located between the barrier layer 440 and the first carry substrate410 a, as shown in FIG. 3B. After the first wring layer 420 a and thebarrier layer 440 are formed, fabrication of the first wiring carryingsubstrate 400 a′ is finished.

Material of the first wring layer 420 a is different to that of thebarrier layer 440. The material of the first wiring layer 420 a is forexample copper, and the material of the barrier layer 440 is for examplenickel. Moreover, the method of forming the first wiring layer 420 a andthe barrier layer 440 is the same to that of the first wiring layer 220a of the aforementioned embodiment, and therefore detailed descriptionthereof is not repeated.

FIG. 3B to FIG. 3D mainly disclose a method of forming a plurality offirst blind via B3. Referring to FIG. 3B and FIG. 3C, after the firstwiring layer 420 a and the barrier layer 440 are formed, a part of themask layer 430 is removed to form a plurality of openings O, wherein theopenings O partially expose the surface S1 of the first carry substrate410 a.

Method of removing a part of the mask layer 430 includes removing a partof the mask layer 430 by using laser beam, and the laser beam can beprovided by a carbon dioxide laser device, an ultra violet laser deviceor a YAG laser device.

Referring to FIG. 3C and FIG. 3D, a part of the first carry substrate410 a in the openings O is removed to form a plurality of first blindvia B3. Depth of the first blind via B3 can be greater than a thicknessof the metal layer 414 a, as shown in FIG. 3D. Certainly, according tothe first blind via B1′ disclosed in FIG. 2B, the depth of the firstblind via B3 of the present embodiment can also be less than thethickness of the metal layer 414 a.

Method of removing a part of the first carry substrate 410 a includesetching the first carry substrate 410 a. In detail, after the openings Oare formed, the mask layer 430 and the barrier layer 440 can function asan etching mask. When the first carry substrate 410 a is etched, a kindof etching fluid that can etch the metal layer 414 a without damagingthe mask layer 430 and the barrier layer 440 can be applied. Therefore,the first blind via B3 can be formed without damaging the first wiringlayer 420 a.

It should be noted that quantities the openings O and the first blindvia B3 shown in FIG. 3C and FIG. 3D are more than one, though in otherembodiments that are not illustrated, the quantities of the openings Oand the first blind via B3 can be one. Therefore, the quantities of theopenings O and the first blind via B3 shown in FIG. 3C and FIG. 3D areonly an example, which is not used for limiting the present invention.

Referring to FIG. 3D and FIG. 3E, after the first blind via B3 areformed, the barrier layer 440 and the remained mask layer 430 areremoved to expose the first wiring layer 420 a. Now, fabrication of thefirst wiring carrying substrate 400 a is completed.

Referring to FIG. 3F, the first wiring carrying substrate 400 a islaminated to a second wiring carrying substrate 400 b via an insulationlayer 310, wherein the insulation layer 310 full fills the first blindvia B3. The second wiring carrying substrate 400 b includes a secondcarry substrate 410 b and a second wiring layer 420 b, wherein thesecond wiring layer 420 b is disposed on the second carry substrate 410b. Structure of the first wiring carrying substrate 400 a is similar tothat of the second wiring carrying substrate 400 b, and structure of thesecond carry substrate 410 b is the same to that of the first carrysubstrate 410 a, and therefore detailed descriptions thereof are notrepeated.

Referring to FIG. 3F and FIG. 3G, a part of the first carry substrate410 a and a part of the second carry substrate 410 b are removed toexpose the insulation layer 310 in the first blind via B3. The method ofremoving a part of the first carry substrate 410 a and a part of thesecond carry substrate 410 b is the same to the method of removing apart of the first carry substrate 210 a and a part of the second carrysubstrate 210 b of the aforementioned embodiment, and therefore detaileddescriptions thereof are not repeated.

After a part of the first carry substrate 410 a and a part of the secondcarry substrate 410 b are removed, steps shown in FIG. 2F to FIG. 2G arethen performed, and since the steps shown in FIG. 2F to FIG. 2G havebeen described in the aforementioned embodiment, follow-up steps afterthe step of FIG. 3G are not repeated.

In summary, before the wiring carrying substrate (i.e. the first wiringcarrying substrate) is laminated to the insulation layer, at least oneblind via is preformed on the wiring carrying substrate. When the wiringcarrying substrate is laminated, the insulation layer full fills theblind via. After a part of the carry substrate is removed, theinsulation layer in the blind via is exposed.

Though the insulation layer is deformed during laminating the wiringcarrying substrate, shifting of the relative position (i.e. thelayer-layer shifting) between layouts of the wiring layers (i.e. thefirst wiring layer and the second wiring layer) due to the deformationis controlled within a relatively low level, in which only a whole sizeperformance of the wiring board is changed, and shifting of the relativepositions between the hole (including the conductive through hole andconductive blind via) positions and the layouts of the wiring layers canbe mitigated by marking the correct positions on the exposed insulationlayer in the blind via for the holes to be formed.

Moreover, during formation of the holes, the laser beam which can easilythermally ablate the insulation layer without damaging the carrysubstrate and the wiring layer is applied, for example, the laser beamprovided by the carbon dioxide laser device. Therefore, the holes can beaccurately formed in the blind via.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A wiring board, having at least one hole, thewiring board comprising: an insulating layer has a first surface and asecond surface opposite to the first surface, wherein the at least onehole extends from the first surface to the second surface; a firstwiring layer embedded in the insulating layer at the first surface,wherein the first wiring layer has a first top surface exposed by theinsulating layer and a first bottom surface which is opposite to thefirst top surface and is in contact with the insulating layer; a secondwiring layer embedded in the insulating layer at the second surface,wherein the second wiring layer has a second top surface exposed by theinsulating layer and a second bottom surface which is opposite to thesecond top surface and is in contact with the insulating layer; and atleast a conductive pillar, disposed in the hole, and connected betweenthe first wiring layer and the second wiring layer, wherein theconductive pillar has a pillar top surface exposed by the insulatinglayer at the first surface and a pillar bottom surface which is exposedby the insulating layer at the second surface and is opposite to the topsurface, and the diameter of conductive pillar gradually shrinks from afirst level of the first bottom surface of the first wiring layertowards the pillar top surface.
 2. The wiring board as claimed in claim1, wherein the conductive pillar full fills the hole.
 3. The wiringboard as claimed in claim 1, wherein an interface is respectivelyexisted between the conductive pillar and the first wiring layer, andbetween the conductive pillar and the second wiring layer.
 4. The wiringboard as claimed in claim 1, wherein the hole is a through hole, thediameter of a portion of the conductive pillar between the first wiringlayer and the second wiring layer in the insulation layer is uniform andthe diameter of conductive pillar gradually shrinks from a second levelof the second bottom surface of the second wiring layer towards thepillar bottom surface.